Method and apparatus for delivering information to an idle mobile station in a group communication network

ABSTRACT

A method and apparatus provides for delivering information to an idle mobile station in a group communication network includes delivering the information to the mobile station in special form, e.g., short data burst (SDB) form, if the information is smaller than a predetermined size limit. In one embodiment, the method and apparatus provides for encapsulating the information inside a frame, forwarding the frame to a server for delivery to the mobile station, and causing the server to extract the information from the frame and deliver the information to the mobile station on a forward common channel. In one embodiment, the method and apparatus provides for receiving information for delivery to the mobile station, the information being tagged for delivery on a forward common channel, and delivering the information to the mobile station on the forward common channel. In one aspect, the method delivers the information when the mobile station is in idle state with no traffic channel.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/291,454, filed May 15, 2001. This application isalso related to U.S. patent application Ser. No. 09/518,622, filed Mar.3, 2000. These applications are incorporated herein by reference intheir entirety.

FIELD

The present invention relates to point to multi-point communicationssystems. More specifically, the present invention relates to a methodand apparatus for delivering information to an idle mobile station in agroup communication network.

BACKGROUND

A class of wireless service intended for quick, efficient, one-to-one orone-to-many (group) communication has existed in various forms for manyyears. In general, these services have been half-duplex, where a userpresses a “push-to-talk” (PTT) button on his phone/radio to initiatespeech. Pushing the button either keys his radio, in someimplementations, or in a moderated system, where communications occursvia a server of some type, indicates the user's request for the “floor.”If granted the floor, or talker permission, the user then generallyspeaks for a few seconds, after which he releases his PTT button, andother speakers can request the floor. Communication is generally fromone speaker to a group of listeners, but may be one-to-one. This servicehas traditionally been used in applications where one person, a“dispatcher,” needs to communicate to a group of people, such as fieldservice personnel or taxi drivers, which is where the “dispatch” namefor the service comes from.

Recently, similar services have been offered on the Internet and aregenerally known as “voice chat.” These services are usually implementedas personal computer applications that send vocoder frames in Internetprotocol (IP) packets, i.e., voice-over-IP (VoIP) service, to a centralgroup chat server, or possibly from client to client in a peer-to-peerservice.

A key feature of these services is that communication is quick andspontaneous, usually initiated by simply pressing a PTT button, withoutgoing through a typical dialing and ringing sequence. Communication inthis type of service is generally very short, with individual talk“spurts” being generally on the order of several seconds, and“conversations” lasting possibly a minute or less.

The time delay between when the user requests the floor and when hereceives a positive or negative confirmation from the server that he hasthe floor and may begin speaking, which is known as the PTT latency, isa critical parameter for half-duplex group communications systems. Asmentioned previously, dispatch systems place a priority on short, quickconversations, which makes the service less effective if the PTT latencybecomes large.

Existing group communication infrastructures provide limitedopportunities for significantly reducing the PTT latency, i.e., actualPTT latency may not be possibly reduced below the time required tore-establish traffic channels within dormant packet-data sessions.Further, talker and listeners traffic channels are brought up in series,because the only mechanism available to begin waking up a dormant groupis to wait for the talker's traffic channel to be re-established tosignal the server. Currently, no mechanism exists to sendmobile-originated user signaling data on anything other than a trafficchannel—a limitation that requires traffic channels to be re-establishedbefore any communication between clients and the server can take place.

There is a need, therefore, for mechanisms to reduce both apparent PTTlatency experienced by the talker and total time required tore-establish traffic channels for participating mobiles withoutnegatively impacting system capacity, client battery life, or otherresources.

SUMMARY OF THE INVENTION

The disclosed embodiments provide a novel and improved method andapparatus for delivering information to an idle mobile station in agroup communication network. In a first aspect of the invention, amethod for delivering information to an idle mobile station in a groupcommunication network includes the steps of determining whether theinformation is smaller than a predetermined size limit and deliveringthe information to the mobile station on a forward common channel if theinformation is smaller than the predetermined size limit. In one aspect,the information is delivered, e.g., in short data burst (SDB) form, whenthe mobile station is in idle state with no traffic channel.

In a second aspect of the invention, the method for deliveringinformation to an idle mobile station in a group communication networkincludes the steps of encapsulating the information inside a frame,forwarding the frame to a server for delivery to the mobile station, andcausing the server to extract the information from the frame and deliverthe information to the mobile station on forward common channel. In oneaspect, the information is delivered, e.g., in short data burst (SDB)form, when the mobile station is in idle state with no traffic channel.

In a third aspect of the invention, the method for deliveringinformation to an idle mobile station in a group communication networkincludes the steps of receiving information for delivery to the mobilestation, the information being tagged for delivery on a forward commonchannel and delivering the information to the mobile station. In oneaspect, the information is delivered, e.g., in short data burst (SDB)form, when the mobile station is in idle state with no traffic channel.

In one aspect, an apparatus for delivering information to a mobilestation in a group communication network includes a memory unit, areceiver, a transmitter, and a processor communicatively coupled withthe memory unit, the receiver, and the transmitter. The processor iscapable of carrying out the steps of the above-mentioned methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings in which like reference charactersidentify correspondingly throughout and wherein:

FIG. 1 illustrates a group communications system;

FIG. 2 illustrates how several communication devices interact with acommunications manager;

FIG. 3 illustrates call-signaling details for a floor-control requestprocess according to one embodiment;

FIG. 4 illustrates call-signaling details for a network-initiateddormancy-wakeup process according to one embodiment;

FIG. 5 illustrates buffering media at a communications manager sideaccording to one embodiment;

FIG. 6 illustrates buffering media at a client side according to oneembodiment; and

FIG. 7 illustrates exemplary radio-link modes according to oneembodiment.

DETAILED DESCRIPTION

Before one embodiment of the invention is explained in detail, it is tobe understood that the invention is not limited in its application tothe details of the construction and the arrangement of the componentsset forth in the following description or illustrated in the drawings.The invention is capable of being implemented in other embodiments andare carried out in various ways. Also, it is understood that thephraseology and terminology used herein is for purpose of descriptionand should not be regarded as limiting.

FIG. 1 illustrates an exemplary functional block diagram of a groupcommunication system 100. The group communication system 100 is alsoknown as a push-to-talk system, a net broadcast service (NBS), adispatch system, or a point-to-multi-point communication system. In theNBS 100, a group of communication device users, individually known asnet members, communicate with one another using a communication deviceassigned to each net member. The term “net” denotes a group ofcommunication device users authorized to communicate with each other.

In one embodiment, a central database may contain informationidentifying the members of each particular net. More than one net mayoperate in the same communication system. For instance, a first net maybe defined having ten members and a second net may be defined, havingtwenty members. The ten members of the first net may communicate witheach other, but may not communicate with members of the second net. Inanother embodiment, members of different nets are able to monitorcommunications between members of more than one net, but may be onlyable to transmit information to members within their own net.

A net may operate over an existing communications system, withoutrequiring substantial changes to the existing infrastructure. Thus, acontroller and users on a net may operate in any system capable oftransmitting and receiving packet information using Internet protocol(IP), such as a Code Division Multiple Access (CDMA) system, a TimeDivision Multiple Access (TDMA) system, a Global System for MobileCommunications (GSM) system, satellite communication systems such asGlobalstar™ or Iridium™, or a variety of other systems.

Net members may communicate with each other using an assignedcommunication device, shown as communication devices (CDs) 102, 104, 106and 108. CDs 102, 104, 106 and 108 may be wireline or wirelesscommunication devices such as terrestrial wireless telephones, wirelinetelephones having with push-to-talk capability, satellite telephonesequipped with push-to-talk functionality, wireless video cameras, stillcameras, audio devices such as music recorders or players, laptop ordesktop computers, paging devices, or any combination thereof. Forexample, the CD 102 may comprise a wireless terrestrial telephone havinga video camera and display. Furthermore, each CD may be able to send andreceive information in either a secure mode, or a non-secure (clear)mode. Throughout the following discussion, reference to an individual CDinfers a wireless push-to-talk phone. However, it should be understoodthat reference to a CD is not intended to be limited as such, and mayencompass other communication devices that have the capability totransmit and receive packet information in accordance with the InternetProtocol (IP).

In the NBS system 200 of FIG. 2, a transmission privilege generallyallows a single user to transmit information to other net members at agiven time. The transmission privilege is granted or denied to arequesting net member, depending on whether or not the transmissionprivilege is currently assigned to another net member when the requestis received. The process of granting and denying transmission requestsis known as arbitration. Arbitration schemes may evaluate factors suchas priority levels assigned to each CD, the number of unsuccessfulattempts to gain transmission privilege, the length of time a net memberhas held transmission privilege, or other factors, in determiningwhether a requesting net member is granted the transmission privilege.

In order to participate in the NBS system 100, CDs 102, 104, 106, and108 each may have the ability to request transmission privilege from acontroller or a communications manager (CM) 110. CM 110 may manage thereal-time and administrative operation of nets. The CM is any type ofcomputer type device having at least one processor and memory. In oneembodiment, the CM is a Sun Workstation Netra T1™.

CM 110 may operate remotely through either a communication systemservice provider, net members, or both, assuming that authorization isprovided by the service provider. CM 110 may receive net definitionsthrough an external administration interface. Net members may requestadministrative actions through their service provider or administratenet functions through defined systems, such as a member-operatedsecurity manager (SM) 112 that conforms to a CM administrationinterface. CM 10 may authenticate the party who attempts to establish ormodify a net.

SM 112 may perform key management, user authentication, and relatedtasks to support secure nets. A single group communication system mayinteract with one or more SM 112. SM 112 may not be involved in thereal-time control of a net, including net activation or PTT arbitration.SM 112 may have administration capabilities compatible with CM 110interface to automate administration functions. SM 112 may also becapable of acting as a data endpoint for the purpose of participating ina net, broadcast net keys, or simply monitor net traffic.

In one embodiment, the means for requesting the transmission privilegefrom a CM comprises a push-to-talk (PTT) key or switch. When a user inthe NBS 100 desires to transmit information to other net members, theuser may depress the push-to-talk switch located on his or her CD,sending a floor-control request to obtain the transmission privilegefrom CM 110. If no other net member is currently assigned thetransmission privilege, the requesting user may be granted thetransmission privilege and the user may be notified by an audible,visual, or tactile alert through the CD. After the requesting user hasbeen granted the transmission privilege, information may then betransmitted from that user to the other net member.

In one embodiment of the present invention, each wireless net memberestablishes a forward link and a reverse link with one or more basestations 116 or a satellite gateway 118, as the case may be. Basestation 116 may be used to describe a communication channel from basestation 116 or satellite gateway 118 to a CD. Satellite gateway 118 maybe used to describe a communication channel from a CD to base station116 or satellite gateway 118. Voice and/or data may be converted intodata packets, using a CD, for example, which are suitable for aparticular distributed network 120 through which communications to otherusers may take place. In one embodiment, distributed network 120 is theInternet.

In one embodiment, a dedicated forward channel is established in eachcommunication system, i.e., a terrestrial communication system and asatellite communication system, for broadcasting information from eachnet member to the other net members. Each net member may receivecommunications from other net members over the dedicated channel. Inanother embodiment, a dedicated reverse link is established in eachcommunication system for transmitting information to CM 110. In oneembodiment, a combination of the above schemes may be used. For example,a scheme may involve establishing a dedicated forward broadcast channelbut requiring wireless CDs to transmit information to CM 110 over adedicated reverse link assigned to each CD.

When a first net member wishes to transmit information to other membersof the net, the first net member may request the transmission privilegeby pressing a push-to-talk key on his or her CD, which generates arequest formatted for transmission over the distributed network 120. Inthe case of CDs 102 and 104, the request may be transmitted over the airto one or more base stations 116. A mobile switching center (MSC) 122,which may include a well-known inter-working function (IWF), packet dataserving node (PDSN), or packet control function (PCF), for processingdata packets may exist between BS 116 and the distributed network 120.For CD 106, the request is transmitted via satellite gateway 118. For CD108, the request may be transmitted through the public switchedtelephone network (PSTN) 124 to a modem bank 126. Modem bank 126receives the request and provides it to distributed network 120. An NBSterminal 128 monitors traffic of the NBS system through its connectionto distributed network 120. Since NBS terminal 128 is connected to thedistributed network 120, geographic proximity to net participants is notnecessary.

If no other member currently holds the transmission privilege, when theCM 110 receives a transmission privilege request, CM 110 may transmit amessage to the requesting net member, notifying it that the transmissionprivilege has been granted. Audio, visual, or other information from thefirst net member may then be transmitted to the other net members bysending the information to CM 110, using one of the just-describedtransmission paths. In one embodiment, CM 110 then provides theinformation to the other net members by duplicating the information andsending each duplicate to the other net members. If a single broadcastchannel is used, the information need only be duplicated once for eachbroadcast channel in use.

In an alternative embodiment, CM 110 is incorporated into MSC 122 sothat data packets from supporting base stations are routed directly toCM 110 without being routed onto distributed network 120. In thisembodiment, CM 110 is still connected to distributed network 120 so thatother communication systems and devices may participate in a groupcommunication. In yet another embodiment, the CM may be incorporatedinto the PDSN or the PCF modules of the MSC.

In one embodiment, CM 110 maintains one or more databases for managinginformation pertaining to individual net members as well as to eachdefined net. For example, for each net member, a database may compriseinformation such as the user name, account number, a telephone number,or dial number, associated with the member's CD, a mobile identificationnumber assigned to the CD, the current member's status in the net, suchas whether the member is actively participating in the net, a prioritycode for determining how the transmission privilege is assigned, a datatelephone number associated with the CD, an IP address associated withthe CD, and an indication of which nets the member is authorized tocommunicate with. Other related types of information may also be storedby the database with respect to each net member.

In one embodiment, the CD may form connections of individualcommunication terminals to form one talk group, or net. The CM maycomprise a variety of functional capabilities in hardware and softwarethat are configurable in different ways to accommodate differentapplications. The CM may provide capability to manage real-time,administrative, and authenticity operations of (NBS) nets, push-to-talk(PTT) request arbitration, maintenance and distribution of netmembership and registration lists, call set-up and tear-down ofnecessary communication, e.g., CDMA, systems and network resources, aswell as overall control of net status.

The NBS net may be within a stand-alone deployable cellular system, or alarge multiple site configuration. In the case of a large configuration,multiple CMs may be deployed geographically to form a single, integratedsystem, each operating as a plug-in module into existing cellularinfrastructure. As such, new features introduced by NBS nets areavailable to cellular users without requiring modification to existingcellular infrastructure.

The CM may maintain a list of defined NBS nets. In one embodiment, eachnet definition includes a net identifier, a list of members, includingphone numbers or other identifying information, user priorityinformation, and other generic administration information. Nets may bestatically defined as either clear or secure, and transitions betweenclear and secure may not be permitted. A secure NBS net typically usesmedia encryption to provide authentication and guard againsteavesdropping. Media encryption for secure nets is implemented on anend-to-end basis, meaning encryption and decryption may take placewithin the communication device. The CM may operate without knowledge ofsecurity algorithms, keys, or policies.

FIG. 2 illustrates an exemplary NBS net 200 for showing how acommunication device 202 interacts with a CM 204. Multiple CMs may bedeployed as desired for large-scale NBS nets. In FIG. 2, CD 202 haspermission to transmit media to other members of the net. In this case,CD 202 is known as the talker and transmits media over a channel. WhenCD 202 is designated as the talker, the remaining net participants, CD206 and CD 208, may not have permission to transmit media to the net.Accordingly, CD 206 and CD 208 are designated as listeners.

As described above, CD 202, 206, and 208 are connected to CM 204, usingat least one channel. In one embodiment, the channel is divided intoseparate channels comprising a session initiation protocol (SIP) channel210, a NBS media signaling channel 212, and a media traffic channel 214.SIP channel 210 and NBS media signaling channel 212 may be used at anytime as bandwidth allows by any of the CDs 202, 206, and 208, regardlessof being designated a talker or a listener. The SIP is an Internetengineering task force (IETF) defined application-layer protocol thatdescribes control mechanisms to establish, modify, and terminatemultimedia sessions operating over Internet protocol (IP). SIP providesa general solution to call-signaling problems for Internet telephonyapplications by supporting mechanisms to register and locate users,mechanism which define user capabilities and describe media parameters,and mechanisms to determine user availability, call setup, andcall-handling.

In one embodiment, SIP channel 210 is used to start and endparticipation of a CD within the NBS net 100. A session descriptionprotocol (SDP) signal may also be used within SIP channel 210. When theCD's participation within the NBS net is setup, e.g., by using SIPchannel 210, real-time call control and signaling between the CD and theCM takes place, e.g., by using NBS media signaling channel 212. In oneembodiment, NBS media signaling channel 212 is used to handlepush-to-talk requests and releases, arbitrate between conflictingrequests, or floor control, announce the beginning and end ofinformation transmission, manage net dormancy, track endpointconnectivity, request and exchange net status, and notify any errormessages. The protocol of NBS media signaling channel 212 minimizes thelength of most common messages, and simplifies the task of interpretingreplies and responding to requests while retaining flexibility forfuture enhancements. The protocol of NBS media signaling channel 212also allows requests to be resent without adversely affecting protocolstate.

In one embodiment, signaling traffic on NBS media channel 212 includescall setup and control signaling, which may consist of sessioninvitation requests and acknowledgements, and media signaling, which maycomprise of real-time floor control requests and related asynchronousmessages. Media traffic on the media traffic channel 214 may comprise ofreal-time point-to-multi-point voice and/or data broadcasts. Bothmessaging categories have unique functional attributes. In addition,each CD may issue domain name service (DNS) client requests tofacilitate mapping fully qualified DNS hostnames to Internet networkaddresses.

In one embodiment, the NBS call-setup and call-control signaling isperformed according to SIP semantics. Although SIP may be transportedusing either the well-known user datagram protocol (UDP) or transmissioncontrol protocol (TCP), in one embodiment, each CD performs SIP basedsignaling functions using UDP. Also, each CM may expect to receive SIPsignaling requests via UDP. Real-time signaling may occur via dynamicUDP/IP interface on the CM and each CD. Other signaling may take placevia a fixed TCP/IP interface between the CM and the CD using the SIP,for example.

PTT Latency

In one embodiment, when the packet data service is active, resources inthe infrastructure, e.g., base station transceiver subsystem (BTS), basestation controller (BSC), inter-working (IWF), and the radio link areactively assigned to the mobile station (MS). In an IP-based VoIPdispatch service, while there is an active conversation going on betweengroup participants, the packet data connection for each user remainsactive. However, after a period of inactivity, i.e., “hang time,” in thegroup communications the user traffic channels may transition to thedormant state.

The transition to the dormant state conserves system capacity, reducesservice cost and battery drain, and makes the user available to receiveincoming conventional voice calls. For example, when the user is in anactive packet data call, he will generally be considered to be “busy” toincoming voice calls. If the user's packet data call is in the dormantstate, the user may be able to receive incoming voice calls. For thesereasons, it is desirable to transition the packet data call to thedormant state after periods of packet data inactivity.

While packet data calls are active, even if no data packets are beingexchanged, radio frequency (RF) energy may still be transmitted by themobile phones, albeit at a low level, to maintain synchronization andpower control with the base station. These transmissions may cause asignificant power drain on the phone. In the dormant state, however, thephone may not perform any RF transmission. To conserve phone power andextend battery life, the hang time may be set to transition the phone todormant mode after extended periods of no data transmission.

While the packet data service is active for all users, PTT requests,which may be IP datagrams sent between the MS and the dispatch server,have very low latency. However, if the user channels have previouslytransitioned to the dormant state, the PTT latency may be much longer.During packet data dormancy, state information associated with thepacket data session, including the mobile IP address, may be maintained.However, state information associated with layers below PPP, such as thephysical traffic layers, may be released and/or de-allocated.

In some infrastructures, to wake up a dormant data connection, thetraffic channel must be reallocated, the resources must be reassigned,and the radio link protocol (RLP) layer must be reinitialized. Theeffect of this is that after a talk group has not talked for a while,when a user presses his PTT button to request the floor, the PTT latencyfor the first talk spurt is generally much longer than for subsequenttalk spurts. While this is relatively infrequent, it can affect theutility of the service, and should be minimized.

In one embodiment, when the group communication devices are in thedormant state, PTT latency may be caused by the following:

-   -   1. Talker Channel Assignment Delay—Delay in assigning and        initializing a traffic channel for the talker's phone in        response to a user pushing a push-to-talk button and the        dispatch application initiating an IP-based floor-request        message.    -   2. Floor Request Propagation Delay—Time for a floor-request        message to propagate to the dispatch server.    -   3. Arbitration Delay—Time for the dispatch server to process        potentially multiple floor requests.    -   4. Wakeup Message Delay—Time for the IP messages from the        dispatch server to propagate to the cellular infrastructure,        e.g., PDSN, serving the listener.    -   5. Listener Paging Delay—Time delay due to the requirement to        wait for the listener's phone to wake up and receive a page in        the appropriate paging channel slot.    -   6. Listener Channel Assignment Delay—Delay in assigning and        initializing the traffic channels of the listeners' phones.    -   Some of these delays are more significant than others in their        contribution to the overall PTT latency. For instance, the        talker and listener channel assignment latencies, and the        listener paging latency are often an order of magnitude greater        than the other components, and together drive the ultimate PTT        latency performance.

To reduce the PTT latency, in one embodiment, the group call signaling,such as the floor-control requests, floor-control responses, anddormancy wakeup messages, may be transmitted on some available commonchannels, without waiting for dedicated traffic channels to bere-established. Such common channels may be always available, regardlessof the state of the mobiles, and may not require being requested andreassigned each time a user wishes to initiate a group call. Therefore,the group call signaling may be exchanged even when mobiles are dormant,which may provide a means to re-establish dedicated traffic channels forthe talker and listener mobiles in parallel.

In one embodiment, the calling mobile may send a floor-control requestto the wireless infrastructure over some available reverse commonchannels, such as reverse access channel and reverse enhanced accesschannel. The calling mobile may also receive a response to thefloor-control request on some available forward common channels, such asforward paging channel and forward common control channel. In oneembodiment, the dormant listener mobiles may receive dormancy wakeupmessages on some available forward common channels, such as forwardpaging channel and forward common control channel.

Short Data Burst Call-Signaling Messages

In one embodiment, a significant reduction in the actual total dormancywakeup time and the PTT latency perceived by the talker, may be achievedthrough the use of the short data burst (SDB) messages, as provided in“TIA/EIA/IS-2000 Standards for cdma2000 Spread Spectrum Systems,”hereinafter referred to as “the cdma2000 standard,” for example. In oneembodiment, SDB messages may be sent over both dedicated physicalchannels, such as the forward fundamental channel (FCH) or forwarddedicated common control channel (F-DCCH), or common physical channels,such as the reverse access channel (R-ACH), reverse enhanced accesschannel (R-EACH), forward common control channel (F-CCCH), or pagingchannel (PCH). SDB messages may be transported by radio burst protocol(RBP), which maps the messages onto an appropriate and availablephysical layer channel. Because SDB messages may carry arbitrary IPtraffic and may be sent over common physical channels, SDB messagesprovide a mechanism to exchange group call signaling when a callingclient's mobile has no dedicated traffic channels.

Mobile-Originated Call-Signaling Messages

In one embodiment, media-signaling messages may carry IP datagrams overthe reverse link or mobile-originated link. A client mobile station maysignal the CM quickly whenever the user requests the floor and adedicated reverse traffic channel is not immediately available. Assumingthe client mobile station has released all dedicated traffic channels,the client mobile station may immediately forward the floor-controlrequest over a reverse common channel of a wireless infrastructure,which may relay the request to the CM. For example, either the reverseaccess channel or the reverse enhanced access channel may be used tosend such messages when a dedicated reverse channel is not available. Inone embodiment, the client mobile station may transmit a floor-requestmessage to the CM as an SDB Message.

FIG. 3 shows an exemplary call-signaling for a floor-control requestprocess. The client mobile station (MS) may receive a request from auser who wishes to initiate a group call. In one embodiment, the clientMS may be a PTT device. In one embodiment, the client MS may send thePTT floor request 302 over a reverse common channel, such as the accesschannel or enhanced access channel, before attempting to re-establishits dedicated traffic channel. In one embodiment, the client MS may sendthe PTT floor request 302 in a SDB message regardless of what channel isused.

The client MS may then start re-establishing its dedicated trafficchannel 304, e.g., by performing the “service option 33 re-origination,”for example. The client MS may also start radio link protocol (RLP)synchronization 306. In one embodiment, the client MS may re-establishits dedicated traffic channel and synchronize RLP advantageously inparallel with sending the PTT floor request 302.

Therefore, use of the available reverse common channels and/or SDBfeature to signal floor-control requests to the CM, when a mobilestation does not have active dedicated traffic channels, reduces thetotal time required to wake up the participating mobiles. Although thetalker client may not receive confirmation that its floor-request hasbeen granted until the talker's forward traffic channel isre-established, the ability to quickly signal the CM to begin waking upparticipating listeners reduces the overall latency.

Referring to FIG. 3, the wireless infrastructure may send the PTTfloor-control request 308 to packet data service node (PDSN) and then tothe CM. In one embodiment, after receiving the floor-control request310, the CM may arbitrate the request, burst media signaling wakeupmessages (triggers) to a group of target participants (listeners),and/or trigger the re-establishment of participants' (listeners')traffic channels. If the CM grants the PTT floor request, the CM maysend PTT floor grant 312 to the infrastructure, which may send PTT floorgrant 314 to the client MS. In one embodiment, the infrastructure maysend PTT floor grant 314 to the client MS on an available forward commonchannel, such as forward paging channel and forward common controlchannel, if the client's dedicated traffic channel is not re-establishedyet. In one embodiment, the infrastructure may send PTT floor grant 314to the client MS in SDB form regardless of what channel is used.

In one embodiment, the CM may wait for dormancy response timer to expirebefore responding to the PTT floor-control request. If the group'sdormancy response timer is set to zero, the CM may respond to thefloor-control request immediately. In one embodiment, if the client MShas completed re-establishing its traffic channel and RLPsynchronization, the client MS may stream media 316, which may have beenbuffered in the client MS, to the CM.

Network-Originated Call-Signaling Messages

In one embodiment, after receiving the floor-control request, the CM mayburst media signaling wakeup messages to a group of target participants(listeners) and trigger the re-establishment of participants'(listeners') traffic channels. If the group's dormancy response timer isset to zero, the CM may respond to the floor control requestimmediately. In one embodiment, if the talker has began re-establishingits traffic channel immediately upon sending the PTT request, thecaller's and listeners' traffic channels may be advantageouslyre-established in parallel.

FIG. 4 shows an exemplary call signaling for a network-initiateddormancy wakeup process. After the CM receives PTT floor-control request310 (FIG. 3), the CM may send wakeup triggers 402 directed to targetlisteners. The PSDN may determine whether a packet-data session existsfor the target mobile, and forwards the trigger packet to theappropriate infrastructure element, e.g., a base station. Theinfrastructure may page 406 each individual target MS to startre-establishing its dedicated traffic channel. The target MS may thenstart re-establishing its dedicated traffic channel 408, e.g., byperforming the “service option 33 re-origination,” for example. Thetarget MS may also start radio link protocol (RLP) synchronization 410.In one embodiment, the target MSs may re-establish their dedicatedtraffic channels and synchronize their RLPs advantageously in parallelwith same functions being performed by the client MS.

In one embodiment, after a target MS has completed re-establishing itsdedicated traffic channel and synchronizing its RLP, the CM may resendthe wakeup trigger 412 to the target MS. The target MS may send thewakeup reply 414 to the CM, indicating that the target MS is ready toreceive media. The CM may send talker announcement 416 to the client MSbefore streaming media 418, which may have been buffered in the CM, tothe target MS.

In one embodiment, the infrastructure may send the wakeup trigger 412 toa target listener over some available common forward channels, such asforward paging channel and forward common control channel, while thetarget listeners' traffic channels are not re-established yet. In oneembodiment, the infrastructure may send the wakeup trigger 412 to thetarget listener in SDB form, regardless of what channel is used. If thePTT floor-control request is sent on the talker's reverse common channelas a SDB message and the target group's dormancy response timer is setto zero at the CM, actual PTT latency at the talker client may bereduced to the time required to send an SDB request message on thereverse link followed by a SDB response message on the forward link.

Network Interfaces for Call-Signaling Messages

To determine what network-originated specific traffic, e.g., SDBpayload, is sent for an idle mobile station with no dedicated trafficchannels, some infrastructure policy or interface for distinguishingsuch specific traffic from other traffic may be implemented.

In a first embodiment, IP datagrams may be filtered based on theirsizes, as the SDB messages may carry a limited user payload. IPdatagrams smaller than a predetermined size limit may be sent as SDBmessage, if destined for a mobile with no dedicated traffic channels.The group communication system may use such filters, as the applicationfloor-request response message is quite small, e.g., 34 bytes includingthe IP headers.

In a second embodiment, an infrastructure vendor may define an IP-basedservice for encapsulating IP traffic destined for delivery to a mobilestation. An IP server with knowledge of this service may transmit smallIP, e.g., UDP, datagrams, appropriately encapsulated with IP headers, tothis service for delivery to a mobile suspected of not having adedicated traffic channel. The group communication systems may use thisservice to indicate to the infrastructure that the floor-requestresponse message be delivered to the requesting client MS in SDB form,for example. Coordination of SDB traffic with pending pages or serviceorigination requests is also important to insure quick and reliabledelivery of user traffic.

In a third embodiment, an IP server may transmit special IP, e.g., UDP,datagrams with IP headers for delivery to a mobile suspected of nothaving a dedicated traffic channel. The IP server may tag the IPdatagrams, e.g., by designating a special value in the IP header, forinstructing the infrastructure to deliver the IP datagrams to the clientMS. The group communication systems may use this service to indicate tothe infrastructure that the floor-request response message be deliveredto the requesting client MS in SDB form, for example. In a thirdembodiment, a UDP or TCP port range may be reserved for deliveringspecific IP datagrams, e.g., SDB messages.

Mobile-Initiated Service Origination and Paging

In one embodiment, as discussed above in connection with FIG. 3, atalker mobile station (MS) may send a floor-control request 302 to theCM, which may be in SDB form, followed immediately with a serviceorigination request 304 to the wireless, e.g., CDMA, infrastructure forquickly re-establishing its traffic channels. However, if the dormancyresponse timer is set to a small value, the CM may respond to thefloor-control request 310 quickly and transmit a response 312 back tothe talker MS. If this response arrives at the infrastructure during theearly phases of the service origination transaction 304, theinfrastructure notes that the talker MS does not have any active trafficchannel and attempts to page the response to the talker MS. However,this paging action may abort the service origination transaction alreadyin progress. In one embodiment, the talker MS may respond to the page,insuring that the floor-control response message is delivered to thetalker, and request service origination again, but an unnecessary delayis experienced in re-establishing the talker's traffic channel as aresult of the aborted original service origination attempt.

In a first embodiment, to avoid the race condition between the serviceorigination process and paging, the CM may be configured to not respondimmediately to the floor-control request 310. Accordingly, the dormancyresponse timer, e.g., in the CM, may be adjusted so that the CMtransmits the response 312 to the talker MS after the serviceorigination process 304 is complete.

In a second embodiment, the PDSN, which receives the CM-initiatedresponse 312, and the mobile switching center (MSC), which responds tothe talker's service origination request, are coordinated. That is, ifthe PDSN determines that a packet-data service origination process forthe talker MS is already in progress when the CM-initiated response 312arrives at the infrastructure, the MSC may defer paging the talker MS.The PDSN may cache the response and send it over the talker mobile'sforward traffic channel once the service origination process iscomplete. Alternatively, the MSC may send the response to the talker MSas an SDB message if the service origination process is still inprogress.

In a third embodiment, the talker MS may avoid the race condition by notissuing a service origination request 304 until after the talker MS hasreceived a response to the floor-control request 302. In one embodiment,since the talker MS has no active dedicated traffic channel, the CM maysend the response to the talker MS on some available forward commonchannels, such as forward paging channel and forward common controlchannel. In one embodiment, the CM may send the response to the talkerMS in SDB form. The talker MS may rely on the CM-generated floor-controlresponse 312 to trigger its traffic channel re-activation, in the samefashion that the wakeup requests sent by the CM trigger traffic channelre-activation for the listener mobiles. The race condition is avoided asthe potential for simultaneous mobile-initiated service origination andnetwork-initiated paging of the mobile is avoided.

Caching Network-Initiated Packet Data Triggers

The IP datagram, including the wakeup trigger 402, that arrives at thewireless, e.g., CDMA, infrastructure and is destined for a listenermobile that has no dedicated traffic channels may be lost, either by thenetwork in general or by the wireless infrastructure specifically. Inone embodiment, the wakeup trigger 402 sent to the listener mobile isretransmitted aggressively according to a defined schedule until thelisteners respond or the group's wakeup timer expires. For example, thewakeup trigger 402 may be resent every 500 ms. However, retransmittingthe wakeup triggers 402 at this rate may cause a maximum delay of up to500 ms, or an average delay of 250 ms, from the time a listener'straffic channel is re-established to the time next wakeup triggerdestined for that listener arrives at the infrastructure.

In one embodiment, the infrastructure or another entity in the networkmay cache the wakeup trigger 402 sent by the CM, and deliver it to atarget MS as soon as the target MS has re-established its trafficchannel. This eliminates the need for retransmission of wakeup request412 by the CM, and reduces total dormancy wakeup time. Cashing thewakeup trigger 402, as opposed to retransmitting it at the rate of 500ms, for example, may eliminate a delay of up to 500 ms. from the totaldormancy wakeup time.

Media Buffering

In one embodiment, the user may be allowed to start talking after theuser has requested floor control, by buffering the media beforededicated channels are re-established between the client and thelisteners. By buffering the talker's speech, the system allows thetalker to start talking before the listeners' traffic channels have beenfully re-established. This allows the talker to start talking earlier,reducing his apparent PTT latency. Since listeners don't experience PTTlatency, their experience is unaffected, i.e., the PTT latency isshifted from the talker to other parts of the system. The talker maywait just as long to receive a response from a listener to his firsttalk spurt, but as mentioned previously, he already expects the responseto his first talk spurt to take longer than the response to subsequenttalk spurts that occur while he is engaged in an active conversation.Buffering of the talker's first talk spurt can be done on the CM side oron the client MS side.

CM Buffering

In one embodiment, the CM may buffer the talker's first talk spurt.After a user has pressed his PTT button and the user's traffic channelsare re-established, he may be allowed to communicate with the CM. Atthis time, since the listener traffic channels are not yet up, the CMbuffers the talker's speech for future transmission to the targetlisteners. CM buffering may reduce the apparent PTT latency that thetalker sees to the approximate time it takes to bring up the talker'straffic channel. FIG. 5 shows CM buffering according to one embodiment.

Client Side Buffering

In one embodiment, where a shorter apparent latency is desired, thetalker may be allowed to begin speaking before even his traffic channelis re-established. Because the client MS is not yet in communicationwith the CM, the signal to the talker to begin talking is made by theclient MS. If the talker is allowed to speak before the talker's trafficchannel is re-established, the client MS may buffer the speech. Becausecommunication with the CM has not yet been established, permission totalk is being given “optimistically.” FIG. 6 shows client-side bufferingaccording to one embodiment. In one embodiment, both CM buffering andclient-side buffering may operate concurrently. Client-side bufferingmay allow the apparent PTT latency to be small.

As with CM buffering, the total delay may not alter. The user may stillexperience the same delay in receiving a response back from thelistener, but the talker's apparent PTT latency may be made small.

In one embodiment, the client MS may buffer media to control theapparent PTT latency experienced by the user. The combination ofmobile-originated SDB and client-side media buffering may reduce thedelays associated with re-establishing active traffic channels.

Quick Paging Channel

In one embodiment, the CM may delay responding to the talker's PTTrequest until the group's wakeup timer expires or all listener clientshave responded to a network-initiated trigger to bring up theirrespective traffic channels. The CM may wait until all listeners arepaged before allowing the talker to stream media at the group. Thelonger the group's listeners take to respond to the page, the longer thetalker's perceived PTT latency.

In one embodiment, during dormancy wakeup, each listener client isindividually sent a series of wakeup triggers by the CM, which uponarrival at the, e.g., CDMA, infrastructure, trigger one or more pages toeach mobile. After receiving the page, each mobile may re-establish atraffic channel, receive the next wake up request transmitted to it, andrespond to the CM with a wake up request reply. A major component of thetime required by listener handsets to respond to this application level“ping” is spent at the infrastructure waiting for an appropriate time topage the mobile.

To conserve battery life, mobiles may not need to constantly monitoreach of the, e.g., 2048, slots defined within the paging channel whenthe mobiles are in the idle state. Rather, mobiles may monitor eitherthe forward common control channel (F-CCCH) or the forward pagingchannel (F-PCH), depending on the mobile's capabilities. Furthermore,mobiles may monitor the paging slot according to their slot cycle index.

In one embodiment, to conserve battery life, the mobiles may operate in“slotted paging” mode. In this mode, the mobiles wake up periodicallyfor a short time to listen to pages sent by the base station (BS). TheBS, which may know when mobiles will be listening, may send pages to aparticular mobile during the particular paging slots.

In one embodiment, the period that the mobile wakes up to listen to thepaging channel is controlled by a parameter called the slot cycle index(SCI). The larger the SCI, the longer the time between the slots thatthe mobile wakes up to listen to the paging channel. A large slot cyclevalue increases phone standby time, since the phone spends a largerpercentage of its time sleeping, but increases the time the BS mightneed to wait before it can page the phone.

The amount of time the BS may need to delay its page to the phone variesbetween zero, if the phone's slot is just starting when the BS needs topage it, to the full slot cycle, if the phone's slot has just ended whento the BS needs to page the phone. On average, the delay due to waitingfor the phone's slot to come around is half the slot cycle period. Theshorter the slot cycle used by a mobile, the faster a listener may bepaged by the infrastructure. However, a shorter slot cycle may imply ahigher rate of battery drain.

In one embodiment, the forward quick paging channel (F-QPCH) may be usedto allow the mobile to determine, in a power-efficient manner, when apending page is present without requiring that the mobile monitor thepaging channel itself. A mobile that is capable of monitoring the F-QPCHmay wake up every predetermined number of slots to extract the value ofa one-bit indicator within a, e.g., 80 ms, slot on the paging channel.If the extracted bit is not set, no page is pending on the pagingchannel and the mobile sleeps for another slot cycles. If the extractedbit is set, a page for that mobile may be pending and the mobile mayschedule itself to wake up and monitor the paging channel at the nextappropriate paging channel slot.

The modulation employed by F-QPCH allows the mobile to monitor theF-QPCH much more efficiently than it can monitor the paging channel.This allows the mobile to effectively operate at a very short slot cyclein a power-efficient manner. One advantage of using the F-QPCH is toprovide the mobile with the means to detect and respond to general pagemessages from the infrastructure, and hence wakeup request messages fromthe CM, at a faster slot cycle than would otherwise be allowed at thesame battery drain rate. This in turn translates to the ability tominimize one component of the delay that contributes directly to PTTlatency and the total dormancy wakeup time-the time required tore-establish listener traffic channels.

Slotted Timer

In one embodiment, the mobiles may operate in a non-slotted paging modein conjunction with a “slotted timer.” When activated, the slotted timerrequires the mobile to monitor the paging channel in a non-slotted modeupon releasing its dedicated traffic channels and entering the idle modefor a period of time defined by the slotted timer. The value of thistimer is configurable at the base station. This feature allows theinfrastructure to instruct the mobile to monitor every, e.g., 80 ms,slot on the paging channel when in the idle mode and provides a meansfor the infrastructure to page the mobile in any slot. As in the case ofusing the quick paging channel feature alone, one advantage of using thenon-slotted mode is to provide a means for the mobile to detect andrespond to pages more quickly than would otherwise be allowed at thesame battery drain rate, and hence to reduce the time required tore-establish listeners' traffic channels during dormancy wakeup.

Without the quick paging channel feature, extended use of non-slottedmonitoring may be expensive on battery life. However, using the quickpaging channel and non-slotted mode together provides a means to page amobile almost immediately—within one or two slot periods, e.g., 80 to160 ms.

Non-slotted mode can be viewed as one of two intermediate stages ofdormancy available to a mobile station. When operating in non-slottedmode, a mobile may be considered technically dormant because it has nodedicated physical channels. However, in this mode the mobile may bepaged essentially immediately in any slot, and thus the paging delayassociated with network-initiated reactivation is avoided.

Control-Hold Mode

In one embodiment, the mobiles may operate under a packet data standardthat provides an additional dormant/idle state in which the mobile andinfrastructure maintain the PPP layer state associated with the mobilewhile allowing either endpoint to release the dedicated traffic channelsand other resources associated with the mobile's packet-data serviceoption call. Either the mobile or the infrastructure may transition thestate of the packet data call from dormant/idle state to active state byre-establishing a traffic channel and renegotiating RLP. The timerequired to re-establish the traffic channel may be dependent on whetherthe mobile or the infrastructure initiates the re-establishment.However, in both cases the delay is comparable to that required tooriginate a new call on the system, as essentially all system resourcesmay need to be requested and allocated to the mobile.

In one embodiment, the mobiles may operate in a “control-hold” mode thatoperates as an interim position between the active and idle modes. Incontrol-hold mode, the dedicated traffic channels associated with themobile may be released and the mobile's reverse pilot may operate in“gated” mode. In one embodiment, the dedicated common control channeland/or the RLP state may also maintained. In essence, the control-holdmode offers a semi-dormant state in which most system resources mayremain allocated, but the average reverse-link transmission power isreduced to a gated pilot in order to reduce the impact to systemcapacity. FIG. 7 shows an exemplary arrangement for radio modes.

In one embodiment, mobiles may transition from active mode tocontrol-hold mode by sending either a resource release request messageor a resource release request mini message. Mobiles may transition fromcontrol-hold mode to active mode by sending either a resource requestmessage or a resource request mini message. These messages may betransported via the dedicated control channel, and the mini-messages maybe sent using shorter, e.g., 5 ms, frames, allowing fast transitionsinto and out of control-hold mode. On advantage of the control-holdmode, compared to the traditional idle mode or the dormant/idle mode, asdescribed above, is the relatively fast transition possible fromcontrol-hold mode to active mode.

In one embodiment, upon receiving an indication from the CM that asubscribed group has transitioned to the group-dormant state, a clientmobile may initially transition itself to the control-hold mode and,after an additional sustained period of inactivity, make a furthertransition to the idle mode. Therefore, control-hold mode offers amechanism to significantly reduce the time required to re-establishdedicated traffic channels once a user presses PTT or a wakeup requesttrigger is received at the infrastructure.

Stored Service Configuration

In one embodiment, the infrastructure may provide the ability to cacheor store service configuration state at the mobile and infrastructurewhen transitioning to idle mode. When returning back to the active modeand re-establishing traffic channels, the mobile may indicate, in eitherthe origination message or page response message, that it has cached orstored a service configuration for the call. The mobile may also includein the origination or page response message a cyclic redundancy check(CRC) that may be calculated over the entire length of the serviceconfiguration. If the base station has also cached the serviceconfiguration, the base station may use the received CRC to confirm thatits service configuration matches the mobile's stored serviceconfiguration and, if so, the BS may indicate in its “service connectmessage” that the mobile may use the previously stored serviceconfiguration.

In one embodiment, the use of the packet-data service option may notrequire service configuration changes when transitioning out of the idlemode, and hence use of the stored service configuration may result in asignificant reduction in the time-required to re-establish dedicatedtraffic channel resources. Therefore, the stored service configurationfeature implements an important enhancement to the idle mode byproviding a mechanism to significantly reduce PTT latency by reducingthe time required to re-establish traffic channels which may carry bothPTT signaling and related media.

In one embodiment, the transition to the idle mode from the active modefor a client MS may be implemented as follows:

-   -   1. The group is active and the mobile has dedicated traffic        channels.    -   2. After a period of inactivity exceeding the group's hang time        timer, an application layer group-dormant announcement is        received over the mobile's forward traffic channel.    -   3. The mobile transitions to the control-hold mode, caching the        state of its service configuration. Likewise, the client's base        station also caches the state of the service configuration.    -   4. After a period of inactivity, the mobile releases its        dedicated channel and transitions to the idle mode. The mobile        begins monitoring the quick paging channel and may enter        non-slotted mode if instructed by the infrastructure. If the        period of inactivity is relatively short—either due to the local        user pressing PTT or network-originated packet data traffic from        another group participant—the mobile may not reach the idle mode        before transitioning back to the active mode. In this case, the        transition back to the active mode occurs quickly, as the mobile        has retained its dedicated channel.

In one embodiment, the dormancy wakeup event may be implemented asfollows:

-   -   1. The group is dormant and all the mobiles are idle with no        dedicated physical channels. The mobiles are monitoring the        quick paging channel.    -   2. In response to a user pressing push-to-talk, the talker's        mobile signals the CM with an application layer floor-request        message over some available reverse common channel, which may be        in short data burst form. The talker's mobile may begin        buffering user media from this point forward.    -   3. The talker's mobile sends an “origination message” to the        infrastructure to re-establish its traffic channel. It may        indicate in its request that it has cached the service        configuration and may include a CRC over the configuration data.        This begins the process of re-establishing the talker's mobile        traffic channel.    -   4. The CM receives the floor-request and decides whether to        grant the request or not, through an arbitration process and        sends floor-request response messages to the talker. The CM also        begins bursting a series of wakeup requests to all participants.    -   5. Upon receipt of each wakeup request, the infrastructure pages        each listerner's mobile by first determining the next        appropriate slot in which to page the listerner's mobile and        then signaling via the F-QPCH prior to that slot that a page        will be pending on the paging channel for that listerner's        mobile.    -   6. Upon receipt of an indication on the F-QPCH that a page is        pending, each listener mobile monitors the paging channel for a        page.    -   7. Upon receipt of a page on the paging channel, each listener        mobile responds to the page, indicating in its page response        that it has cached the service configuration and may include a        CRC over the configuration data. This begins the process of        re-establishing each listener's traffic channel.    -   8. After establishment of the talker's traffic channel, the next        floor-request response from the CM is received at the talker.        The talker begins streaming media to the CM.    -   9. After establishment of each listener's traffic channel, the        next wakeup request sent by the CM is received at the listener.        The listener replies with a wakeup response message.    -   10. Once all listeners have responded or the group's wakeup        timer expires, the CM begins streaming media to the group.

Therefore, the herein disclosed embodiments for a method and apparatusfor reducing latency in a group communication network provides for asignificant reduction in the actual total dormancy wakeup time and thePTT latency by exchanging group call signaling even when mobiles aredormant and no traffic channel is active. The method and apparatusprovides for exchanging the group call signaling through the use of theshort data burst (SDB) message signaling. The method and apparatusprovides for re-establishing dedicated traffic channels for the talkermobile and the dormant listener mobiles advantageously in parallel.

In another embodiment, the dormant-wakeup latency in a groupcommunication network may be reduced through caching thenetwork-initiated wakeup triggers destined for target listeners, anddelivering a wakeup trigger to a target mobile station as soon as thetarget mobile station has re-established its traffic channel.

In another embodiment, simultaneous service origination and paging in amobile operating in a group communication network is avoided bytransmitting a response to a floor-control request after the serviceorigination process is complete. In one embodiment, the response to thefloor-control request may be in SDB form if the service originationprocess is not complete. In another embodiment, the service originationprocess for the source communication device is initiated aftertransmitting the response to the source communication device.

1. A method for delivering information to a mobile station in a groupcommunication network for a push-to-talk communication, the methodcomprising: encapsulating the information inside a frame; forwarding theframe to a server for delivery to the mobile station; and causing theserver to extract the information from the frame and deliver theinformation to the mobile station on a forward common channel to bereceived by all mobile stations monitoring said forward common channelfor a push-to-talk communication.
 2. The method of claim 1, wherein thecausing the server to deliver the information includes causing theserver to deliver the information when the mobile station is in idlestate with no traffic channel.
 3. The method of claim 1, wherein causingthe server to deliver the information includes causing the server todeliver the information on a forward paging channel (F-PCH).
 4. Themethod of claim 1, wherein causing the server to deliver the informationincludes causing the server to deliver the information on a forwardcommon control channel (F-CCCH).
 5. The method of claim 1, whereincausing the server to deliver the information includes causing theserver to deliver the information in short data burst (SDB) form.
 6. Acomputer-readable medium comprising at least one instruction, which,when executed by a machine, causes the machine to perform operations,the instructions comprising: a set of the instructions to encapsulatethe information inside a frame; a set of the instructions to forward theframe to a server for delivery to the mobile station; and a set of theinstructions to cause the server to extract the information from theframe and deliver the information to the mobile station on a forwardcommon channel to be received by all mobile stations monitoring saidforward common channel for a push-to-talk communication.
 7. Thecomputer-readable medium of claim 6, wherein the set of the instructionsto cause the server to deliver the information includes a set of theinstructions to cause the server to deliver the information when themobile station is in idle state with no traffic channel.
 8. Thecomputer-readable medium of claim 6, wherein the set of the instructionsto cause the server to deliver the information includes a set of theinstructions to cause the server to deliver the information on a forwardpaging channel (F-PCH).
 9. The computer-readable medium of claim 6,wherein the set of the instructions to cause the server to deliver theinformation includes a set of the instructions to cause the server todeliver the information on a forward common control channel (F-CCCH).10. The computer-readable medium of claim 6, wherein the set of theinstructions to deliver the information includes a set of theinstructions to deliver the information in short data burst (SDB) form.11. An apparatus for delivering information to a mobile station in agroup communication network for a push-to-talk communication,comprising: means for encapsulating the information inside a frame;means for forwarding the frame to a server for delivery to the mobilestation; and means for causing the server to extract the informationfrom the frame and deliver the information to the mobile station on aforward common channel to be received by all mobile stations monitoringsaid forward common channel for a push-to-talk communication.
 12. Theapparatus of claim 11, wherein the means for causing the server todeliver the information includes means for causing the server to deliverthe information when the mobile station is in idle state with no trafficchannel.
 13. The apparatus of claim 11, wherein means for causing theserver to deliver the information includes means for causing the serverto deliver the information on a forward paging channel (F-PCH).
 14. Theapparatus of claim 11, wherein the means for causing the server todeliver the information includes means for causing the server to deliverthe information on a forward common control channel (F-CCCH).
 15. Theapparatus of claim 11, wherein the means for causing the server todeliver the information includes means for causing the server to deliverthe information in short data burst (SDB) form.
 16. A system fordelivering information to a mobile station in a group communicationnetwork for a push-to-talk communication, comprising: a receiver toreceive information over the network; a transmitter to transmitinformation over the network; and a processor communicatively coupledwith the receiver and the transmitter, the processor operable to:encapsulate the information inside a frame; forward the frame to aserver for delivery to the mobile station; and cause the server toextract the information from the frame and deliver the information tothe mobile station on a forward common channel to be received by allmobile stations monitoring said forward common channel for apush-to-talk communication.
 17. The system of claim 16, wherein theprocessor is further operable to cause the server to deliver theinformation when the mobile station is in idle state with no trafficchannel.
 18. The system of claim 16, wherein the processor is furtheroperable to cause the server to deliver the information on a forwardpaging channel (F-PCH).
 19. The system of claim 16, wherein theprocessor is further operable to cause the server to deliver theinformation on a forward common control channel (F-CCCH).
 20. The systemof claim 16, wherein the processor is further operable to cause theserver to deliver the information in short data burst (SDB) form.